With two large eyes and a white, 120-centimeter body, Pepper is being billed as the first robot that can sense human feelings. Mr. Son calls it “the robot that makes its own decision to act with love.”

“For the first time in the history of humans and the history of robots, today is the day we take up the challenge of giving emotions to robots,” Mr. Son said at a packed news conference. “Today will be a historic day when you look back hundreds of years from now,” he said, adding that he had been dreaming of giving robots a heart for 25 years.

Pepper had a few words of its own.

“Being able to be considerate is my most important function,” said the robot, who will begin working in a public relations role at Softbank stores in the upscale Tokyo neighborhoods of Ginza and Omotesando on Friday.

With so many cameras flashing, Pepper became concerned about Mr. Son, asking: “Aren’t you dizzy?”

Its creators envisioned it playing the role of babysitter, party promoter, and most importantly, family member. Mr. Son said Pepper would be able to learn the routines and hobbies of family members — as well as gather information about their moods. It would then save this information to a new cloud data base set up by Softbank.

Pepper did seem to do pretty well at assessing Mr. Son’s character. As he introduced the robot with a smile, Pepper said: “With such a great smile, you will be successful in big business.”

While Pepper was created to seem human in the way it moves and speaks, it has only one leg. But that means it can function for 12 hours without recharging, compared with 30 minutes to an hour for robots with two legs, Mr. Son said.

Pepper will be sold to individual customers for ¥198,000 (around $1,950) from February 2015 at Softbank stores and online in Japan, and eventually worldwide. But Mr. Son said making money from Pepper wasn’t the main priority.

“We will ignore profits at the beginning,” he said. “I want as many families as possible to have the robot, so I am sticking to a price similar to personal computers.”